<html>
<script>
function test(){


	setTimeout(function(){
		var el = document.getElementById("div");
 		el.style.borderLeft = "10px"; //1次重排版
  		el.style.borderRight = "20px"; //又1次重排版
  		el.style.padding = "50px"; //还有1次重排版
	}, 2000);
	
}
</script>
<body onload = "test()";>
	<div id="div">
		dd
	</div>
	</body>
</html>